Roller cam assembly

ABSTRACT

A two-stage epicyclic roller cam transmission comprising in each stage: a roller ring having a plurality of fixed-position rollers; and a cam gear having pitch-circle-generated, trochoid-shaped teeth and independent pitch, wherein the rollers are spaced to mesh with the cam gear and efficiently transfer energy under heavy loads.

BACKGROUND OF THE INVENTION

Early prime movers or power sources such as the mill stream water wheel;and, later the steam engine, created a need for transferring power fromone place to another through torque transfer. An early example of torquetransfer was the belt and pulley assembly, frequently utilized inmachine shops to drive various machines.

The early prime movers generated low revolutions per minute (rpm) andmechanically simple torque transfer mechanisms were capable of creatingvery little power. In portable machines, chains and sprockets are oftenused to transfer power. The most common example of this form of torquetransfer is the ordinary bicycle. The bicycle sprocket and chain are aroller cam assembly; and the relative motion between the roller in thechain and the sprocket is that of an involute. It is the shape of thesprocket that enables the power to be transferred smoothly.

With the need to transfer torque between adjacent parallel andperpendicular shafts, something else had to be devised. In fact, the oldwater wheels that were used to grind grain employed wooden pegs as gearteeth to transfer torque; but, as rpm and torque increased, it wasobserved that a fluctuation in speeds occurred, creating destructiveforces. This fluctuation resulted from the variations during rotation ofthe effective radii between the meshing of the pegged wheels.

The variation of the effective radii was a result of the shape of thepegs. The first solution was to develop a double cycloid tooth with aconvex shape above the pitch circle and a concave shape below the pitchcircle. These gears looked something like a plurality of rollers evenlyspaced with their axes parallel to the input shaft and attached to thesurface of a wheel. If two concave arcs were placed near the point ofattachment and the surface of the wheel, it would create a tooth thatresembled the teeth used in these gears. This design solved the velocityfluctuations. However, the gears were difficult to manufacture and theirshape made them highly susceptible to failure.

In the latter part of the nineteenth century, the involute gear wasdeveloped. It was both much stronger and cheaper to make. Incalculations of gear strength, the teeth were treated as a series ofcantilevered beams, and an engineer named Lewis devised a table ofvalues called the Lewis Form Factor that simplified calculations oftorque capacity of spur gears. This table is used in calculations today.

1. Field of the Invention

The present invention utilizes the parameters of existing spur gearssuch as a choice of pitch and pitch circle in a meshing “rollerring-toothed cam” configuration that employs roller action as opposed tothe high-friction sliding action of spur gear. In the present invention,it is the trochoidal shape that eliminates the interference betweenmeshing members. This configuration permits fewer, larger and strongerteeth in the smaller meshing member and allows the design of smaller,stronger and more compact gear trains. Fewer, larger teeth are possiblebecause the shape of the cam tooth is determined by the relative motionbetween rotating bodies.

A roller ring-toothed cam combination can be designed with externalmeshing members, internal meshing members, bevel gear arrangements andrack and pinion combinations. In all of these proposed assemblies,either the larger or the smaller member can be the roller ring or thetoothed cam. The point to be made here is that any of the rollerring-toothed cam assemblies disclosed herein will permit the design ofcompact, high-strength gear trains with very high train values and purerolling contact.

2. Description of the Prior Art

In U.S. Pat. No. Re. 17,811 issued Sep. 23, 1930, the inventoridentified the point on the cam shape where the shape changes fromconcave to convex.

He noted that this point on the curve would carry the load, caused bythe contact of the roller for a longer period of time. To overcome thisdwell problem, he utilized a prolate trochoid curve where the generatingpoint is three-fourths the distance from the center of the generatingcircle compared to the radius of the generating circle. This distancemust also equal the eccentricity of the crank. The dwell point is apoint on the cam that has a zero radius of curvature arid this pointcannot support loads without deteriorating the cam. For this reason,cycloidal curves should not be used in roller cams. By locating thegenerating point so far from the surface of the generating pitch circle,the effective component of the forces between the roller and the cam isgreatly reduced. thereby severely limiting the capacity of this priorart mechanism to handle torque. U.S. Pat. No. 5,247,847 dated Sep. 28,1993 is particularly relevant to the instant disclosure. It describesthe use of roller cams for external assemblies where the roller ring isalways smaller, in a rack and pinion assembly where the roller ring isthe pinion; and in a torque assembly where the roller cam is in a bevelgear design. The definition and description of the roller cams in thisreference utilize a mathematical presentation with the line of centersbeing held constant and the two rotating members being rotated. Thisprocedure follows the historical graphical procedure using conjugatecurves. Furthermore, this procedure can develop the same shaped tooththat is created by the use of epicycloidal mathematics described herein.In the latter case, one of the pitch circles is held stationary whilethe line of centers and the other pitch circle, with the generatingpoint, is allowed to rotate. In both cases, the tooth shapes generatedare identical. The practical problem with these epicycloidal andcycloidal tooth shapes is that there is one point on the face of eachtooth that has a zero-radius of curvature. And this point will nothandle any forces without inflicting serious deterioration on the camsurface.

Two additional references that are somewhat relevant to the disclosedinvention include U.S. Pat. No. 3,783,712 dated Jan. 8, 1974, whichdiscloses a roller cam assembly employing a long arcing slot containingtwo suspended rollers that are separated by a wedge to fill the slot andtransmit torque; and U.S. Pat. No. 4,604,916 dated Aug. 12, 1986, whichuses a free floating set of rollers on a retaining ring as used inroller bearings. This ring of rollers has one more roller than the innermember has notches and one less roller than the outer member has notchesand all rollers are in contact with both the inner member and the outermember at all times.

SUMMARY OF THE INVENTION

This invention discloses a transmission having a roller cam assemblythat utilizes a pair of drive shafts, one an input shaft and the otheran output shaft, wherein one of said shafts is attached to a toothed camhaving a trochoidal profile and the other drive shaft is attached to aroller ring having a plurality of attached cylindrical roller shaftsaligned to mesh with said toothed cam and thereby permit the transfer oftorque from one shaft to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated axial view of a curtate epitrochoidal cam androller ring assembly wherein the axis of the cam is within or inside thepitch circle of the roller ring.

FIG. 2 is the same view as FIG. 1, in partial section, showing aone-half pitch clockwise displacement from FIG. 1.

FIG. 3 is an elevated side view of FIG. 1 after rotating the roller camassembly 90° in the horizontal plane.

FIG. 4 is an elevated axial view of a prolate epitrochoidal cam androller ring assembly wherein the axis of the cam is outside the pitchcircle of the roller ring.

FIG. 4 a is an enlarged view of the epitrochoid cam of FIG. 4 showingthe strobbed motion of a solitary roller's relative motion across theface of the cam.

FIG. 4 b is a further enlargement of a single pitch of the cam of FIG. 4a, which more clearly depicts how the profile of the cam perfectlymatches the relative motion of the roller.

FIG. 5 is the same view as FIG. 4, in partial section, but showing aone-half pitch deviation from FIG. 4.

FIG. 6 is an elevated side view of FIG. 4 after rotating the roller camassembly rotated 90° in the horizontal plane.

FIG. 7 is an elevated axial view of a prolate epitrochoidal cam androller assembly wherein the axle of the cam is located inside the pitchcircle of the roller ring.

FIG. 8 is an elevated axial view of a curtate epitrochoidal cam androller assembly wherein the axis of the cam is external to the pitchcircle of the roller ring.

FIG. 8 a is the is the curtate epitrochoid cam of FIG. 8 showing theincremental motion of a solitary roller's relative motion across theface of the cam.

FIG. 8 b is an enlarged view of a single pitch of the cam of FIG. 8depicting subsections (I-V) of the roller's interaction with the cam.

FIG. 9 is an elevated axial view of a prolate hypotrochoid cam androller ring assembly.

FIG. 10 is an elevated axial view of a curtate hypotrochoid cam androller ring assembly.

FIG. 11 is an elevated axial view of a prolate hypotrochoidal cam androller ring assembly with an eccentric axle on the roller ring.

FIG. 12 is an elevated axial view of a curtate hypotrochoidal cam androller ring assembly with an eccentric shaft on the roller ring.

FIG. 13 is a two-stage hypotrochoidal reverted epicyclic roller ringassembly wherein the input and output shafts are in the plane of thepage.

FIG. 14 is a curtate trochoidal cam roller ring assembly that changesrotary motion into linear motion

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An understanding of the disclosed roller cam assembly can be bestappreciated by referring to the drawing. This disclosure describes fourdifferent types of trochoid cam profiles that can interact efficientlywith appropriately matched roller ring assemblies. These cam profilescan be described either mathematically or mechanically. This documentwill do both. The cams can be located internal to the circumference ofthe roller ring assembly (see FIGS. 1 & 7). Or they can be locatedexternally to the circumference of the roller ring assembly (see FIGS. 4& 8). Additionally, the cam can also surround the roller ring as inFIGS. 9-12. When the cam is internal or external to the roller ringassembly, but not surrounding the roller ring assembly, it is anepitrochoid cam. In this disclosure, the cams and roller rings move thesame as with the gears. The cam shape controls the relative motionbetween them so as to generate the same output as gears. Herein aredescribed two types of epitrochoidal cams namely, curtate (FIG. 1) andprolate (FIG. 4). Similarly, we will describe two types of rollerring-surrounding cams namely, curtate hypotrochoidal (see FIGS. 10 & 12)and prolate hypotrochoidal (see FIGS. 9 & 11). Furthermore, thetrochoidal cam and roller ring arrangement lends itself to use inepicyclic transmissions as depicted in FIGS. 11 & 12.

FIG. 1 shows an axial view of a curtate epitrochoidal cam and rollerring assembly 10 wherein the input shaft 28 and the output shaft 14 areoffset and project into and out of the plane of the page. In thisfigure, “A” represents the input torque on the roller ring 24 asdelivered by the roller ring input shaft 28. This clockwise torque “A”will drive the curtate epitrochoid cam 12 in a clockwise directionresulting in a reduced output torque “B” which is transferred to theoutput shaft 14. Because there are more roller elements 26 on the inputroller ring than teeth on the cam 12, this configuration represents anoverdrive transmission in which a 0.67 turn on the input shaft 28results in 1.0 turn of the output shaft 14. The pitch circle of the cam12 and roller ring 24 are represented by the circles labeled 21 & 31respectively. The pitch circles contact and turn on each other withoutslipping at the 12 o'clock position. The pitch of the cam 12 and theroller ring 24 is represented by the value of “X” where the indicatedradii cross the pitch circle 21 of the cam 12. Reference 27 is intendedto indicate that the rollers can consist essentially of a sleeve with abushing for high loading or any of a variety of commercially availablecantilevered rollers with internal roller bearings for lower loadapplications and reduced frictional losses. These designs do not excludethe use of rollers with end supports. In this disclosure, end supportsare not included in the drawing to simplify the figures and thevisualizations of the designs.

Upon closer inspection of FIG. 1, the range of roller pin 26interactions with the cam 12 is apparent. The cam position 22 depictsthe initial contact or driving interaction between the roller pin 26 andthe cam tooth 30. Similarly, the cam position 20 shows the final contactregion between the cam tooth 30 and the roller pin 26. The interactionbetween the roller pin and a curtate epitrochoid cam is fairly complexand will be explained in detail by referring to FIG. 8 b. Briefly, theinteracting roller pin makes several transitions from driving 22 toholding 17 to a neutral or nodal position 18 back to a driving position19 and to a final holding interaction in position 20. Such intricateinteractions are not obvious upon a casual scanning of the figures.

FIG. 2 depicts the roller cam assembly rotated one-half X or one-halfpitch from the position shown in FIG. 1. Note the positions M and N,which represent the initial and final positions of roller pin 26interaction with cam 12. When FIGS. 1 and 2 are conceptually combined, abetter appreciation of the roller pin 26 and cam 12 interaction isrealized. Note the displacement of the roller pin centers inside thepitch circle of the cam 21. This radial displacement is a controllingfactor in dictating the curtate epitrochoidal cam profile shown in FIGS.1 and 2. This displacement inside 31 is defined by the term epsilon inthe curtate epitrochoid profile-defining equations, infra.

FIG. 3 offers a longitudinal perspective wherein the roller cam assembly10 in FIG. 1 has been rotated 90° in the horizontal plane such that thecam shaft 14 and the roller ring shaft 28 are now in the plane of thepage. The compactness of this curtate epitrochoid cam and roller ringdesign is clearly seen in this view.

FIGS. 4, 5, & 6 represent a series of views parallel to FIGS. 1, 2, & 3except that the cam design is a prolate epitrochoid type and the camaxis is located outside the circumference of the roller ring assembly24. FIG. 4 is an axial view of a prolate epitrochoid cam and roller ringassembly 10 wherein the input shaft 14 and the output shaft 28 areoffset and project into and out of the plane of the page. In this figure“A” represents the input torque on the cam 12 as delivered by the inputcam shaft 14. This clockwise torque A will drive the roller ringassembly 24 in a counter clockwise direction resulting in a increasedoutput torque “B”, which is transferred to the roller ring output shaft28. Because there are more roller elements 26 on the output roller ringthan teeth on the input cam 12, this configuration represents atransmission in which 1.0 turn on the input shaft 14 results in 0.5 turnof the output shaft 28. The pitch circles of the cam 12 and roller ring24 are represented by the circles labeled 21 & 31 respectively. Thepitch circles contact and turn on each other without slipping at the 6o'clock position of the cam. Note that the roller pin centers aredisplaced inwardly from the roller ring pitch circle 31 or outward fromthe pitch circle of the cam 21. This inward displacement of the rollerpin centers from the roller ring pitch circle is similarly thecontrolling factor for defining the prolate epitrochoid cam profile.This displacement is defined as epsilon in the prolate epitrochoiddefining equations infra. The pitch of the cam 12 and the roller ring 24is designated by the value “X” as measured along the pitch circle.

FIGS. 4 a and 4 b clearly show that the profile of the prolateepitrochoid cam is such that it completely defines the relative motionof the roller pin center across the cam. In this view the cam is held inplace and the roller ring pitch circle is rotated around the cam pitchcircle. From the beginning to the end of the pitch cycle, the roller pin26 is in continuous contact with the cam 12.

In contrast to the curtate epitrochoid cam (FIGS. 1-3), the initialroller contact at position (O) FIG. 4 of the driving prolate epitrochoidcam 12 (also see FIGS. 4-6) provides a holding action as opposed to adriving action. Similarly, the final interaction of the driving prolateepitrochoidal cam with the roller ring 24 is a driving contact (seeFIGS. 4, 4 a, & 4 b). Halfway between positions O and P is a neutral ornodal point in the roller pin's interaction with the cam (see FIG. 4).At the neutral position the cam is not driving or holding back theroller pin. In FIG. 4 the driving face of the cam tooth 16 and theholding face of the cam tooth are identified by 22 and 20, respectively.

The contacting pitch circles of the cam and roller ring are representedby the circles labeled 21 and 31, respectively. Note that the roller pincenters are displaced inwardly from the roller ring pitch circle 31 oroutward from the pitch circle of the cam 21. This inward displacement ofthe roller pin centers from the pitch circle is similarly thecontrolling factor for defining the prolate epitrochoid cam profile.This displacement is defined as epsilon in the prolate epitrochoiddefining equations, infra.

FIG. 5 illustrates an alternate view of FIG. 4 wherein the cam has beenrotated clockwise one-half pitch. In FIG. 5 the unique feature ofprolate epitrochoid cams is clearly revealed by showing that the singleengaged cam tooth is simultaneously driving and holding the roller ringand minimizing back-lash by holding back the next roller pin to bedriven. An advantage in this design is the minimization of theintermittent motion which is more likely with involute gear designs.

FIG. 6 gives a longitudinal perspective wherein the roller cam assembly10 in FIG. 4 has been rotated 90° so that the cam shaft 14 and theroller ring shaft 28 are now in the plane of the page.

FIGS. 7 & 8 show that the roller ring-epitrochoid cam relationshipsdescribed in FIGS. 1-3 and FIGS. 4-6 can be reversed with respect to thelocation of the cam shaft, viz. the same cam can work with two uniqueroller rings. The roller rings are clearly different depending onwhether the cam is located inside or outside of the roller ring'scircumference. Compare FIGS. 4 & 7 and 1 & 8.

FIGS. 8A and 8B show close-up and extreme close-up views of theincremental motion of an individual roller pin 26 across the curtateepitrochoid cam 12 in FIG. 8. This motion can be duplicated by holdingthe cam still and rotating the roller ring around the cam at a distanceequal to the sum of the cam and roller ring pitch circle radii. In thesefigures the cam is rotating with a clockwise driving torque B. With thecurtate epitrochoid cam, the relative motion of the roller pin acrossthe cam is not intuitively obvious. Therefore, this motion is shown inextreme close-up with the phases of roller cam contact indicated byRoman numerals I-V (FIG. 8B). The initial roller pin 26 and cam contacttakes occurs along a holding face of the cam tooth 22 designated phaseI. The roller pin then departs from the initial contact tooth at a pointdesignated 30 and then traverses the notch and contacts the next camtooth on a driving face 17 designated phase II. Driving occurs duringphase II as the roller traverses down the cam tooth until the rollerreaches the bottom of the tooth or the notch 18, designated phase III.At this point the roller is not driving or holding. It is in a nodalposition. During phase IV the roller traverses up the holding cam face19 until it reaches position 30. At this point the roller ceases itsholding action and again traverses the notch and contacts anotherdriving face of the adjacent cam tooth. This final driving phase isdesignated phase V. We call this unique motion across the cam a “gammamotion” after the Greek character that it simulates. This complex motionwith two phases of driving and two phases of holding within a singlepitch cycle has not been described before and enables this design todramatically reduce intermittent action. Normally, more than one rollercontacts the cam in a given instance and thus holding and driving phaseson adjacent cam teeth and rollers are overlapping. This overlapminimizes intermittent action in these cam and roller ring designs.Other designs that have claimed to eliminate intermittent action haverequired continuous contact between a rolling elements and the cams toachieve this end (Distin et al. U.S. Pat. No. 4,584,904).

FIG. 9 illustrates a second form of roller cam assembly 10, namely theprolate hypotrochoid cam design. With hypotrochoid cams the roller ringassembly 24 is contained within, or surrounded by, the cam 12. In thisfigure the roller ring shaft 28 is the input shaft imparting a torque“A” to the roller ring assembly. This action applies a torque “B” to thecam 12, which is attached to shaft 14, and is 1.5 times greater than“A”. In an identical fashion to the prolate epitrochoid cam (see FIG. 4Band its description). This hypotrochoid cam provides an initial holdingaction upon first contact with the roller ring and a driving actionfollowing the nodal position at six o'clock in FIG. 9. Consequently,this hypotrochoid design also has all the benefits of the prolateepitrochoid cam-roller ring design such as reduced friction, eliminatedinterference, and minimized intermittent action. The circles labeled 31and 21 represent the pitch circles of the roller ring and camrespectively.

FIG. 10 appears quite similar to FIG. 9 because it also is ahypotrochoid cam roller ring assembly. However the centers of therollers are displaced in a radial fashion outside the pitch circle ofthe roller ring 31 by an amount ε. This difference manifests itself onthe shape of the cam, requiring it to be a curtate hypotrochoid in orderto control the relative motion of the roller ring as it interacts withthe cam as described in FIG. 8B.

FIGS. 11 & 12 simply extend these hypotrochoid cam and roller ringassemblies into an epicyclic design wherein the roller ring is mountedon an eccentric shaft of displacement Y (eccentricity) as it rotatesaround its axis 33. Also note that in FIGS. 11 and 12 the cams arefixed, and the eccentric and the roller ring rotate in oppositedirections. As shown in previous epicyclic gear designs these designscan provide massive gear train values with correspondingly large torquemultiplication. The epicyclic hypotrochoid roller cam assemblies andepicyclic epitrochoid roller cam assemblies shown in FIGS. 11 and 12ideally handle these high train values and high torque values. The stoutcam tooth profiles provide significant strength advantages overconventional involute gears. Furthermore, all the designs portrayed inthis document avoid a point of zero radius of curvature, which isinherent in cycloids.

FIGS. 11 & 12 are intended to be first stages of a two-staged epicyclicconfiguration. In a two-staged configuration the second stage is intandem and mirrors the first stage FIG. 13. Please note that the firststage cam is part of the housing, and also note that the roller rings ofboth stages are firmly attached to each other and that the second stagecam is free to rotate. The out put shaft, which is firmly attached tothe second stage cam, provides the output torque. This arrangement willalso work for epitrochoidal cams. The second stage can be slightlylarger or smaller with the planetary roller rings connected. The secondstage cam is free to rotate around an output shaft that lines up withthe input shaft. These types of staged epicyclic transmissions canprovide very high train values with reduced rotational mass and compactsize.

As an intuitive proof of concept a mechanical means of producing theepitrochoid cams in FIGS. 4 & 8 will be presented: We begin with twoparallel shafts, such as 14 and 28 of FIGS. 4 & 8, spaced as depicted inthe figures. On shaft 14, we install a gear blank of sufficient size toaccommodate cam 14. On shaft 28, we install cylindrical cutters of thesize and placement as the rollers on roller ring 24. Imagine that thecutters have cutting teeth on their sides and ends, such as cutters forend mills. Shafts 14 & 28 are then connected by two spur gears havingidentical pitch circles 31 and 21. The cutters, or the cam blank, are/isconnected to the shaft through splines so that they may be moved axiallyalong the shaft, and they are positioned so that the end mill cuttersface the perpendicular plane of the gear blank. With the cuttersspinning and the shafts rotating, the cutters are brought into the sameperpendicular plane as the gear blank. The resulting cam shape will bethat of cam 12 in FIGS. 4 & 7. The same cam shape can also be generatedhaving the cutters arranged the same as the rollers on roller ring 24 inFIGS. 1 and 8. This method would also work for hypotrochoidal cams suchas those in FIGS. 9 & 10.

In practice, holding the shaft of the roller ring 24 containing thecutters and rotating the “arm” between shafts 14 and 28 in anepicyclical manner, gives the same relative motion as described aboveand would generate cams having the same shape.

Equations

The equations that define the motion of the centers of the roller pinsacross the epitrochoid cams are derived from the equations definingepicyclical motion. In a book entitled: Mechanical design and SystemsHandbook edited by Harold A.Rothbart (McGraw-Hill, New York, 1964) theequation for epicycloid motion is: $\begin{matrix}{x = {{( {a + b} )\cos\quad\phi} - {b\quad\cos\frac{( {a + b} )}{b}\phi}}} \\{y = {{( {a + b} )\sin\quad\phi} - {b\quad\sin\frac{( {a + b} )}{b}\phi}}}\end{matrix}$See page 1-53 for the definitions of the variables. To define theprolate epitrochoid motion a variable ε is added to the equations infra.ε represents an incremental displacement of the generating point(s) forthe cam off the pitch circle of the roller ring assembly towards thecenter of the roller ring. Thus, the equation for the prolateepitrochoid motion produce by the similarly named cam becomes:$\begin{matrix}{x = {{( {a + b} )\cos\quad\phi} - {( {1 - ɛ} )b\quad\cos\frac{( {a + b} )}{b}\phi}}} \\{y = {{( {a + b} )\sin\quad\phi} - {( {1 - ɛ} )b\quad\sin\frac{( {a + b} )}{b}\phi}}}\end{matrix}$Since the curtate epitrochoid cam is generated when the centers of theroller ring are displaced outside the pitch circle of the roller ring,the equation defining this motion becomes: $\begin{matrix}{X = {{( {a + b} )\cos\quad\phi} - {( {1 + ɛ} )b\quad\cos\frac{( {a + b} )}{b}\phi}}} \\{y = {{( {a + b} )\sin\quad\phi} - {( {1 + ɛ} )b\quad\sin\frac{( {a + b} )}{b}\phi}}}\end{matrix}$In a similar manner the equations defining hypotrochoid motion arederived from those equations describing hypocycloidal motion. Againaccording to Rothbart p1-53 those equations are: $\begin{matrix}{x = {{( {a - b} )\cos\quad\phi} + {b\quad\cos\frac{( {a - b} )}{b}\phi}}} \\{y = {{( {a - b} )\sin\quad\phi} - {b\quad\sin\frac{( {a - b} )}{b}\phi}}}\end{matrix}$Again, by amending the above equations with the value ε we can definethe prolate hypotrochoid motion as: $\begin{matrix}{x = {{( {a - b} )\cos\quad\phi} + {( {1 - ɛ} )b\quad\cos\frac{( {a - b} )}{b}\phi}}} \\{y = {{( {a - b} )\sin\quad\phi} - {( {1 - ɛ} )b\quad\sin\frac{( {a - b} )}{b}\phi}}}\end{matrix}$Similarly, we can define curtate hypotrochoid motion as follows:$\begin{matrix}{x = {{( {a - b} )\cos\quad\phi} + {( {1 + ɛ} )b\quad\cos\frac{( {a - b} )}{b}\phi}}} \\{y = {{( {a - b} )\sin\quad\phi} - {( {1 + ɛ} )b\quad\sin\frac{( {a - b} )}{b}\phi}}}\end{matrix}$

While the foregoing is a complete and detailed description of thepreferred embodiments of the disclosed roller cam assembly, it should beapparent that numerous variations and modifications can be employed toimplement the all-important purpose of the assembly without departingfrom the spirit of the invention, which is fairly defined by theappended claims.

1. A two-stage epicyclic roller cam transmission comprising in eachstage: a roller ring having an even number of fixed-position rollers;and a cam gear having an even number of pitch-circle-generated, curtatetrochoid-shaped teeth, and wherein said rollers are spaced to mesh withsaid cam gear, wherein at least one of said roller rings is configuredto rotate.
 2. The transmission according to claim 1, said teeth havingcurtate epitrochoidal profiles.
 3. The transmission according to claim1, said teeth having curtate hypotrochoidal profiles.
 4. Thetransmission according to claim 1, wherein the output of the first stageis one of said roller rings, said one of said roller rings having afirst even number of rollers, and wherein the output of the second stageis one of said cam gears, said one of said cam gears having the firsteven number of teeth.
 5. The transmission according to claim 1, whereinthe output of the first stage is one of said cam gears, said one of saidcam gears having a first even number of teeth, and wherein the output ofthe second stage is one of said roller rings, said one of said rollerrings having the first even number of rollers.
 6. A two-stage epicyclicroller cam transmission comprising in each stage: a roller ring having aplurality of fixed-position rollers; and a cam gear havingpitch-circle-generated, curtate trochoid-shaped teeth; wherein thedifference between the number of said rollers and the number of saidteeth is at least two, wherein at least one of said roller rings isconfigured to rotate.
 7. The transmission according to claim 6, saidteeth having curtate epitrochoidal profiles.
 8. The transmissionaccording to claim 6, said teeth having curtate hypotrochoidal profiles.9. The transmission according to claim 6, wherein each roller ring hasan even number of rollers, and wherein each cam gear has an even numberof teeth.
 10. The transmission according to claim 6, wherein at leastone of said rollers is not in contact with said cam gear at a given timeduring operation of the transmission.
 11. The transmission according toclaim 6, wherein the output of the first stage is one of said rollerrings, said one of said roller rings having a first number of rollers,and wherein the output of the second stage is one of said cam gears,said one of said cam gears having the first number of teeth.
 12. Thetransmission according to claim 6, wherein the output of the first stageis one of said cam gears, said one of said cam gears having a firstnumber of teeth, and wherein the output of the second stage is one ofsaid roller rings, said one of said roller rings having the first numberof rollers.
 13. The transmission according to claim 11, said teethhaving curtate epitrochoidal profiles.
 14. The transmission according toclaim 11, said teeth having curtate hypotrochoidal profiles.
 15. Thetransmission according to claim 11, wherein each roller ring has an evennumber of rollers, and wherein each cam gear has an even number ofteeth.
 16. A two-stage epicyclic roller cam transmission comprising ineach stage: a roller ring having a plurality of fixed-position rollers;and a cam gear having pitch-circle-generated, curtate trochoidal-shapedteeth; wherein at least one of said roller rings is configured torotate.